1. Field of the Invention
The present invention relates to a manually adjustable clutch that may be adjusted without disassembly of the clutch assembly and that provides an externally visible indication of clutch wear.
2. Background Art
A clutch interrupts the transmission of torque from an engine to a multiple speed gear transmission. A clutch assembly has a plurality of plates with friction engaging surfaces that transmit torque when the clutch plates are compressed and stop torque transfer when pressure is released from the clutch plates. Clutches are subject to wear over time and require periodic adjustment to assure a desired clutch engagement position and optimal performance. It is difficult to determine the extent of clutch wear without disassembling the clutch with most clutch assemblies.
Automatically adjusting clutches have been developed that do not require manual adjustment by a mechanic, however, automatically adjusting clutches require complicated mechanical linkages that add cost to the clutch assembly. Automatically adjusting clutches also require additional parts that add weight and may complicate clutch operation.
Manually adjusted clutches require periodic adjustment to provide optimal performance. Currently, manually adjusted clutches may have threaded adjusting rings that interface with the threads embedded in the clutch housing. Adjusting a clutch by moving an adjusting ring relative to a clutch assembly cover may change the orientation of a diaphragm spring within the clutch. The force required to release the clutch is governed by the orientation, or angle, of the diaphragm spring. The orientation of the diaphragm spring at the new, or original, position provides the lowest release load. One of the purposes of adjusting the clutch is to reorient the diaphragm spring to its original position. A gear may be provided that engages gear teeth on an inner diameter of an adjusting ring. The gear may be rotated to drive the adjusting ring and turn the adjusting ring relative to the clutch cover on threads provided between the clutch cover and the adjusting ring. An example of this type of a clutch adjustment mechanism is disclosed in U.S. Pat. No. 4,832,164.
The adjustment mechanism described in the '164 patent does not provide an externally perceptible visual indication of the extent of clutch wear. The adjustment mechanism also does not indicate during the adjustment process if the clutch has been adjusted to a position corresponding to a new clutch installation.
These and other problems and disadvantages are addressed by applicant's invention as summarized below.